JP4911753B2 - Ni-base superalloy and gas turbine component using the same - Google Patents

Description

  The present invention relates to a Ni (nickel) -based superalloy having excellent high temperature corrosion resistance, high temperature oxidation resistance and high temperature strength and a gas turbine component using the same in order to cope with low quality fuels.

Ni-based super heat-resistant alloys are widely used as industrial gas turbine parts, for example, blade materials. Ren 80 and IN 792, which have excellent corrosion resistance, Mar-M247, which has excellent oxidation resistance, and high strength, are known. Yes.
Further, CMSX-11 and the like in which corrosion resistance and strength are aligned by single crystallization of an alloy having a high Cr (chromium) content are also known.

Since these existing Ni-based superalloys do not have the characteristics of high corrosion resistance (Rene80, etc.) and high oxidation resistance, high strength (Mar-M247, etc.) There is a defect that cannot be applied to high efficiency.
In addition, in a case where the corrosion resistance and the strength are aligned by single crystallization of an alloy having a high Cr content (such as CMSX-11), the oxidation resistance is not sufficient and the single crystal material is complicated. There is a problem that the casting yield of the shaped parts is lowered.

In order to eliminate the problems of existing Ni-based superalloys, mass% , Cr 6-12%, Al (aluminum) 4.5-6.5%, W (tungsten) 2-12%, Ta (Tantalum) 2.5 to 10%, Mo (molybdenum) 5.8% or less, Co (cobalt) 0.1 to 3%, Nb (niobium) 0.2 to 3% or less, Re (rhenium) 0.1 4%, Hf (hafnium) 0.3% or less, and the P value calculated by the following formula (1) in mass% is 2350-3280, and the high corrosion resistance is made up of the inevitable impurities and Ni. Strength alloys are known.
^{P = 200Cr + 80Mo-20Mo 2} -250Ti 2 -50 (Ti × Ta) + 15Nb + 200W-14W 2 + 30Ta-1.5Ta 2 + 2.5Co + 1200Al-100Al 2 + 100Re + 1000Hf-2000Hf 2 + 700Hf 3 -2000V-500C-15000B-500Zr ...... (1 )
However, since this high corrosion-resistant high-strength alloy does not contain Ti (titanium), the corrosion resistance in a high-temperature corrosion environment in which oxidation-sulfurization is superimposed is insufficient.

Further, in terms of mass% , Cr 12.0 to 14.3%, Co 8.5 to 11.0%, Mol. 0 to 3.5%, W 3.5 to 6.2%, Ta 3.0 to 5.5%, Al 3.5 to 4.5%, Ti 2.0 to 3.2%, C (carbon) 0.04 -0.12%, B (boron) 0.005-0.05%, Zr (zirconium) 0.001-5ppm, the balance is high columnar corrosion resistance consisting of Ni and inevitable impurities Crystalline Ni-base heat-resistant alloy large castings are known.
However, this large columnar Ni-base heat-resistant alloy casting has an inadequate ratio of Cr—Al—Ti, and therefore cannot achieve both corrosion resistance and oxidation resistance.

Further, in terms of mass% , Co 4.75 to 5.25%, Cr 15.5 to 16.5%, Mo 0.8 to 1.2%, W 3.75 to 4.25%. Al 3.75 to 4.25%, Ti 1.75 to 2.25%, Ta 4.75 to 5.25%, C 0.006 to 0.04%, B 0.01% or less, Zr 0.01% or less, Hf 1% Hereinafter, Ni-based superalloys suitable for single crystal solidification, in which Nb is 1% or less and each component of Ni and impurities is made 100%, are known.
However, this Ni-based superalloy has insufficient oxidation resistance due to too much Cr.

Furthermore, in mass% , Cr 8-14%, Co 3-7%, Al 4-8%, Ti 5% or less, W6-10%, Ta 4-8%, Mo 0.5-4%, Hf 1.4% or less, Zr0 .01% or less, C0.07% or less, B0.015% or less, balance Ni and inevitable impurities, and 5% ≦ Al + Ti, 4 ≦ Al / Ti, W + Ta + Mo ≦ 18% Superalloys are known. However, this Ni-based single crystal superalloy has insufficient corrosion resistance because Ti is insufficient due to the restriction of 4 ≦ Al / Ti.

Also, by mass% , Cr 7-12%, Co 5-15%, Mo 0.5-5%, W 3-12%, Ta 2-6%, Ti 2-5%, Al 3-5%, Nb 2% or less, Hf 2% or less Ni-based superalloys having 0.03 to 0.25% C, 0.002 to 0.05% B and the remaining components being Ni and incidental impurities are known.
However, this Ni-base superalloy is said to have improved the balance between oxidation resistance and corrosion resistance by increasing the Al to Ti ratio, but does not take into account the relationship with elements added for strength improvement.

Furthermore, by mass% , Cr 2 to 25%, Al 1 to 7%, W 2 to 15%, Ti 0.5 to 5%, Nb 3% or less, Mo 6% or less, Ta 1 to 12%, Re 4% or less, Co 7.5 to 25 %, Fe (iron) 0.5% or less, C 0.2% or less, B0.002 to 0.035%, Hf 2.0% or less, Zr 0.02%, and Ni-based alloy containing 40% or more of Ni Are known.
However, this Ni-based alloy does not take into account the relationship between the balance of each element amount and the material characteristics.

  References relating to the background art include Japanese Patent No. 2844376, Japanese Patent No. 3246376, Japanese Patent Laid-Open No. 2002-235135, Japanese Patent Laid-Open No. 7-300639, Japanese Patent Laid-Open No. 5-59473. And JP-A-9-170402.

  The present invention has excellent high-temperature corrosion resistance for dealing with low-quality fuels, and high-temperature oxidation resistance and high-temperature strength for dealing with improved thermal efficiency due to higher temperatures, as part materials for industrial gas turbines, It is an object of the present invention to provide a Ni-base superalloy capable of ensuring a high yield in a precision casting process and a gas turbine component using the same.

In order to solve the above problems, the first Ni-base superalloy according to the present invention is, in mass %, Co 9 to 11%, Cr 9 to 12%, Mo 0 to 1%, W 6 to 9%, Al 4 to 5%, Ti 4-5%, Nb 0-1%, Ta 0-3%, Hf 0.5-2.5%, Re 0-3%, C 0.05-0.15%, B 0.005-0.015%, Zr 0. 05% or less , and the balance consists of Ni and inevitable impurities.
Moreover, Preferably, the mass % of Hf is 0.5 to 1%.

In order to solve the above problems, the second Ni-base superalloy according to the present invention is, in mass %, Co 9 to 10%, Cr 9 to 10%, Mo 0.5 to 1%, W 6 to 8%, Al 4 to 5 %, Ti 4-5%, Ta 2-3%, Hf 0.5-2.5%, Re 1-3%, C 0.05-0.1%, B 0.005-0.01%, Zr 0.02% or less And the balance consists of Ni and inevitable impurities.
Moreover, Preferably, the mass % of Hf is 0.5 to 1%.

In order to solve the above problems, the third Ni-based superalloy according to the present invention is, in mass %, Co 10-11%, Cr 10-12%, W8-9%, Al 4-5%, Ti 4-5%, Nb 0 to 1%, Hf 0.5 to 2.5%, C 0.05 to 0.15%, B 0.005 to 0.015%, Zr 0.01 to 0.05%, the balance being made of Ni and inevitable impurities It is characterized by.
Moreover, Preferably, the mass % of Hf is 0.5 to 1%.

  In order to solve the above problems, the gas turbine component according to the present invention is manufactured using any one of the first to third Ni-base superalloys, preferably manufactured by a unidirectional solidification casting method. Features.

  In the present invention, in order to make high temperature corrosion resistance, high temperature oxidation resistance, and high temperature strength side by side, a large number of alloys are experimentally evaluated, and as a result, the amount of Cr-Al-Ti falls within an appropriate range, and the composition thereof. In the range, it was found that W is effective as an element that contributes to strength improvement and has little adverse effect on corrosion resistance, and further, a structure judged from a solid capacity with respect to a γ (gamma) phase and a γ ′ (gamma prime) phase. It was made in consideration of stability.

According to each Ni-based superalloy according to the present invention, Cr contributes to corrosion resistance in an environment where sulfidation-oxidation is combined, Al generates γ 'phase and contributes to high temperature strength and oxidation resistance, and contributes to corrosion resistance. High-temperature corrosion resistance by adding a strengthening element centered on W, the amount of which is determined in consideration of the contribution to strength improvement and the effect on corrosion resistance. , High temperature oxidation resistance and high temperature strength.
Further, since a sufficiently high strength can be obtained in the state of a columnar crystal material, it is not necessary to assume single crystallization.
In particular, the second Ni-based super heat-resistant alloy is suitable for columnar crystal blades or single crystal blades by unidirectional solidification casting, and can exhibit the characteristics of corrosion resistance-oxidation resistance-strength at a high level. The super heat-resistant alloy is suitable for a polycrystalline wing by normal casting or a columnar crystal wing by unidirectional solidification casting, and can suppress the material cost while maintaining the characteristics of corrosion resistance-oxidation resistance-strength.
Therefore, it is effective for improving the thermal efficiency and reliability of the gas turbine by applying it to the moving blades of an industrial gas turbine for low quality fuel.

  In addition, according to the gas turbine part of the present invention, since the allowable limit range is wide for the strength reduction due to casting defects such as low-angle grain boundaries and high-angle grain boundaries as compared with the single crystal dedicated material, A high yield can be secured in the turbine component casting process.

It is explanatory drawing which shows the result of the high temperature corrosion test of the Ni base superalloy and the existing Ni base superalloy according to the present invention. It is explanatory drawing which shows the result of the high temperature oxidation test of the Ni-base superalloy and the existing Ni-base superalloy according to the present invention. It is explanatory drawing which shows the result of the creep test of the Ni-base superalloy and the existing Ni-base superalloy according to the present invention.

Co increases the solution heat treatment temperature range, but if the content is less than 9 mass% (10 mass% in the third alloy), the effect cannot be obtained, and 11 mass% (in the second alloy). If it exceeds 10 mass% ), precipitation of the γ 'phase decreases and the high-temperature strength decreases.

Cr improves the corrosion resistance particularly in an environment where sulfidation and oxidation are combined, but if the content is less than 9 mass% (10 mass% in the third alloy), the effect cannot be obtained, and 12 mass%. If it exceeds (10 mass% in the second alloy), a TCP (Topologically Close Packed) phase is generated and the high temperature strength is lowered.

Mo improves the high-temperature strength by solid solution strengthening and precipitation hardening, but if the content exceeds 1 mass% , the corrosion resistance decreases.
In the second alloy, the above effect cannot be obtained when the Mo content is less than 0.5 mass% .

W improves the high-temperature strength by solid solution strengthening and precipitation hardening, but if the content is less than 6 mass% (8 mass% in the third alloy), the effect cannot be obtained, and 9 mass% (first If it exceeds 8 mass% ), the TCP phase is generated and the high-temperature strength is lowered.
In addition, W is generally considered to lower the corrosion resistance, but it has been found that there is little adverse effect on the corrosion resistance in the composition range of the present invention.

Al produces a γ 'phase to improve high temperature strength and oxidation resistance. However, if the content is less than 4 mass% , the effect cannot be obtained, and if it exceeds 5 mass% , The amount of crystal γ ′ phase becomes large, so that solution heat treatment becomes difficult, and the corrosion resistance decreases.

Ti improves the corrosion resistance, but if the content is less than 4 mass% , the effect cannot be obtained, and if it exceeds 5 mass% , the oxidation resistance decreases and the heat treatment performance decreases.

Nb dissolves in the γ 'phase and improves the high-temperature strength. However, if the content exceeds 1 mass% , it segregates at the grain boundaries and the high-temperature strength decreases.

Ta improves the high temperature strength by solid solution strengthening and precipitation hardening. However, if the content exceeds 3 mass% , the amount of eutectic γ 'phase becomes large and solution heat treatment becomes difficult.
In the second alloy, the above effect cannot be obtained when the Ta content is less than 2 mass% .

Hf strengthens the grain boundaries and improves the high-temperature strength and ductility, and is effective for grain boundary cracking during DS casting, but if the content is less than 0.5 mass% , the effect is obtained. If it exceeds 2.5 mass% , it segregates at the grain boundaries and the high-temperature strength decreases.

Re increases the high temperature strength by solid solution strengthening and improves the corrosion resistance particularly at a temperature of 900 ° C. or more. However, when the content exceeds 3 mass% , the ductility is inhibited by precipitation of the TCP phase, and Specific gravity is large and expensive.
In the second alloy, the above effect cannot be obtained when the Re content is less than 1 mass% .

C forms carbides and strengthens the grain boundaries, but if the content is less than 0.05 mass% , the effect cannot be obtained, and 0.15 mass% (0.1 mass in the second alloy) % )), Excessive carbides are formed and the high-temperature strength is lowered.

B forms a boride and strengthens the grain boundary. However, if the content is less than 0.005 mass% , the effect cannot be obtained, and 0.015 mass% (0.01 % in the second alloy). If it exceeds mass% ), the ductility and toughness are lowered, the melting point of the grain boundary is lowered, and the high temperature strength is lowered.

Zr reinforces the grain boundaries, but if the content exceeds 0.05 mass% (0.02 mass% in the second alloy), ductility and toughness decrease, lowering the melting point of the grain boundaries, and increasing the high-temperature strength Decreases.
In the third alloy, if the Zr content is less than 0.01 mass% , the above effect cannot be obtained.

Prepared Ni-base superalloys (inventive alloys 1 to 3 and comparative alloys 1 to 3) having the component compositions shown in Table 1 (along with the component compositions of existing alloy 1 (Rene 80H) and existing alloy 2 (Mar-M247)) These Ni-base superalloys were each solidified using a unidirectional solidification casting furnace at a mold drawing speed of 200 mm / h to produce a round bar-like columnar crystal casting.
Next, the following heat treatment was performed to obtain respective Ni-base superalloys.
Heat treatment conditions Solution treatment: 1200 to 1260 ° C, air cooling after holding for 2 hours Aging treatment: 1st stage 1080 ° C, air cooling after holding for 4 hours
Second stage Air cooling after holding at 870 ° C for 20 hours

When the high temperature corrosion test was performed on the obtained test pieces of the present invention alloys 1 to 3 and the existing alloys 1 and 2 under the following conditions, the maximum erosion depth was as shown in FIG.
Test piece shape: Diameter 10 mm, length 100 mm
Test conditions: In a combustion gas in which corrosive components (sulfurized oil, artificial seawater) are added to kerosene fuel, combustion gas temperature is 1050 ° C, air cooling after exposure for 100 hours, repeated 5 times (total 500 hours)

Moreover, when the oxidation test was performed on the obtained test pieces of the present invention alloys 1 to 3 and the existing alloys 1 and 2 under the following conditions, the increase in mass was as shown in FIG.
Specimen shape: Diameter 10mm, length 25mm
Test conditions: air-cooled after exposure to 950 ° C for 500 hours in air

Furthermore, when the creep test was performed on the obtained test pieces of the present invention alloys 1 to 3 and the existing alloys 1 and 2 under the following conditions, the fracture life was as shown in FIG.
Specimen shape: parallel part diameter 4mm, gauge interval 24mm
Test conditions: in air, 900 ° C., 392 MPa

  On the other hand, based on the existing alloy 1, the present invention alloys 1 to 3, the comparative alloys 1 to 3 and the existing alloy 2 have a maximum erosion depth ratio by a high temperature corrosion test, a mass increase ratio by an oxidation test, and a rupture life ratio by a creep test. As a result, it was as shown in Table 2.

As can be seen from FIGS. 1 to 3 and Table 2, the alloy 1 of the present invention is excellent in corrosion resistance, oxidation resistance, and strength, and is particularly suitable for use as a unidirectionally solidified material with an emphasis on strength.
The alloy 2 of the present invention is suitable for use under conditions that place importance on oxidation resistance and strength, and the corrosion resistance is also an allowable range for A heavy oil fuel.
In addition, the alloy 3 of the present invention is suitable for use under conditions that place importance on corrosion resistance.

On the other hand, the existing alloy 1 is widely used as a gas turbine blade material and has excellent corrosion resistance. However, since it has more Cr and less Al than the composition range of the alloys 1 to 3 of the present invention, it has oxidation resistance. Therefore, it cannot cope with the high temperature of the fuel gas for the purpose of improving the thermal efficiency.
In addition, the existing alloy 2 is excellent in oxidation resistance and strength. However, compared with the composition range of the alloys 1 to 3 of the present invention, since Cr and Ti are less and Al is more, the corrosion resistance is low. I can not cope.

On the other hand, Comparative Alloy 1 (substantially corresponds to the composition range described in Japanese Patent Laid-Open No. 5-59473 and Japanese Laid-Open Patent Publication No. 9-170402) has Ti as compared with the composition range of Alloys 1 to 3 of the present invention. Due to the small amount, the corrosion resistance is insufficient.
Comparative alloy 2 (corresponding almost to the composition range described in JP-A-9-170402) has more Cr and less Al and W than the composition ranges of the alloys 1 to 3 of the present invention. Is insufficient.
Further, Comparative Alloy 3 (substantially corresponding to the composition range described in Japanese Patent Laid-Open No. 5-59473) has insufficient Mo in comparison with the composition range of Alloys 1 to 3 of the present invention, and therefore has insufficient corrosion resistance.

  Although the preferred examples of the present invention have been described above in a specific manner, it is obvious that various modifications can be made. Accordingly, it is to be understood that the invention can be practiced otherwise than as specifically described herein without departing from the scope and spirit of the invention.

Claims (6)

By mass %, Co 9-11%, Cr 9-12%, Mo 0-1%, W 6-9%, Al 4-5%, Ti 4-5%, Nb 0-1%, Ta 0-3%, Hf 0.5-2. 5%, Re 0 to 3%, C 0.05 to 0.15%, B 0.005 to 0.015%, Zr 0.05% or less , and the balance consisting of Ni and inevitable impurities Heat resistant alloy. By mass %, Co 9-10%, Cr 9-10%, Mo 0.5-1%, W 6-8%, Al 4-5%, Ti 4-5%, Ta 2-3%, Hf 0.5-2.5%, A Ni-base superalloy characterized by comprising Re 1 to 3%, C 0.05 to 0.1%, B 0.005 to 0.01%, Zr 0.02% or less , and the balance comprising Ni and inevitable impurities. By mass %, Co 10-11%, Cr 10-12%, W 8-9%, Al 4-5%, Ti 4-5%, Nb 0-1%, Hf 0.5-2.5%, C 0.05-0.15 %, B 0.005 to 0.015%, Zr 0.01 to 0.05%, the balance being Ni and inevitable impurities. The Ni-based superalloy according to any one of claims 1 to 3, wherein the mass % of Hf is 0.5 to 1%.   A gas turbine component comprising the Ni-base superalloy according to any one of claims 1 to 4.   The gas turbine component according to claim 5, wherein the gas turbine component is manufactured by a unidirectional solidification casting method.

Images